Lens barrel

ABSTRACT

A lens barrel includes a first group frame supported by two first guide shafts and a second guide shaft such that it is capable of being advanced or retracted, a focus frame, a focus frame holding portion, and a third group frame. The first guide shafts are bonded and supported by the focus holding frame in parallel such that both ends thereof are exposed. The first group frame and the third group frame are supported slidably by both end portions. Further, the second guide shaft supports the focus frame slidably. An end of the second guide shaft is supported through a short fitting length while it is not fixed to the first group frame and the other end thereof is supported slidably by the third group frame through a short fitting length. Therefore, in this lens barrel, the accuracy in advancement and retraction of respective members is excellent and an efficiency of storage space is excellent thereby contributing to reduction of the size, achieving compactness.

This application claims benefit of Japanese Applications No.Hei11-368191 filed in Japan on Dec. 24, 1999 and No. Hei11-368194 filedin Japan on Dec. 24, 1999, the contents of which are incorporated bythis reference.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a frame member supporting structure ofa lens barrel having plural movable frame members.

2. Related Art Statement

In recent years, compact cameras have been reduced in size and employ ahigh-magnification zoom function and other novel functions.Corresponding to these trends, various types of moving frame retractingmechanisms of the lens barrel have been proposed.

For example, in a lens barrel employing the moving frame positioningmethod disclosed in Japanese Patent Application Laid-Open No.HEI4-52629, a bar-like guide member for supporting a third moving frameslidably with respect to first and second moving frames is employed. Thebar-like guide member is fixed to the first or second moving frame suchthat an end or both ends of the bar-like guide member are held by thefirst or second moving frame and the third moving frame is supportedslidably by the guide member.

Because in the aforementioned lens barrel, an end of the bar-like guidemember or both ends thereof are fixed to a movable frame, a space aroundthat fixing portion becomes a waste space. At the same time, this is anobstacle for a disposition space for other structural members. In thecase of a cantilever structure in which an end of the bar-like guidemember is supported, the span of the bar-like guide member is long, sothat the defection thereof is increased. Therefore, it is difficult tomake a thin bar-like guide member, which is an obstacle againstreduction of the size of the lens barrel.

In the lens barrel disclosed in the aforementioned Japanese PatentApplication Laid-Open No. HEI4-52629, a fourth moving frame is supportedsuch that it is capable of being advanced or retracted relative to thethird moving frame. Thus, two other bar-like guide members are providedadditionally. As a result, to hold four moving frames such that they arecapable of being advanced or retracted, four bar-like guide members aredisposed. These guide members are fixed completely to any of the movingframes. Thus, a very highly accurate configuration and dimension aredemanded for the moving frame and the guide members, thereby leading toincrease of part cost. Further, because the quantity of the guidemembers is large, there is also such a problem that it takes long forassembly work.

SUMMARY OF THE INVENTION

The present invention has been achieved to solve the above-describedproblems and an object of the invention is to provide a lens barrelhaving an effect of reducing part cost, which is easy to assemble, whichan excellent space efficiency and which enables a reduction of the size.

The lens barrel according to an aspect of the present invention includesa first frame, a second frame, a third frame, and a first supportingmember both ends of which are fixed to the second frame such that theyare exposed. The first and third frames are supported by the firstsupporting member.

Further, a lens barrel according to another aspect of the presentinvention has a first frame, a second frame, a third frame, a fourthframe, a first supporting member both ends of which are fixed to thesecond frame such that they are exposed and a second supporting memberwhich is supported by the first frame and third frame. The first frameand the third frame are supported by the first supporting member and thefourth frame is supported by the second supporting member.

Other features and benefits of the present invention will be apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a lens barrel according to an embodimentof the present invention;

FIG. 2 is a perspective view showing a state in which a guide shaft anda focus holding frame are supported by a first assembly jig for guideshaft positioning in a lens barrel of the aforementioned embodiment;

FIG. 3 is a perspective view of a second assembly jig for lens/framemember positioning to be applied to the lens barrel assembly of theembodiment;

FIG. 4 is a perspective view of a third assembly jig for lens/framemember positioning to be applied to the lens barrel assembly of theembodiment;

FIG. 5 is a longitudinal sectional view showing an assembly condition ofthe lens barrel using the second and third assembly jigs in the lensbarrel of the embodiment;

FIG. 6A is an enlarged sectional view showing a section of a bondingportion between the lens group and frame member in the lens barrel ofthe embodiment such that the frame member is protruded relative to thelens group;

FIG. 6B is an enlarged sectional view showing a section of a bondingportion between the lens group and frame member in the lens barrel ofthe embodiment such that the lens group is protruded relative to theframe member;

FIG. 6C is an enlarged sectional view showing a section of a bondingportion between the lens group and frame member in the lens barrel ofthe embodiment such that the frame member and the lens group are locatedon substantially the same surface;

FIG. 7 is a longitudinal sectional view after the lens barrel of theembodiment is assembled;

FIG. 8 is a sectional view (partial sectional view) taken along the lineI—I of FIG. 7; and

FIG. 9 is a development view of a cam groove in cam ring applied to thelens barrel of the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is an exploded view of a lens barrel of a preferred embodiment.FIG. 2 is a perspective view showing a state in which a guide shaft anda focus holding frame are supported by a first assembly jig for guideshaft positioning in a lens barrel of the aforementioned embodiment.FIG. 3 is a perspective view of a second assembly jig for lens/framemember positioning of the lens barrel. FIG. 4 is a perspective view of athird assembly jig for lens/frame member positioning of the lens barrel.FIG. 5 is a longitudinal sectional view showing an assembly condition ofthe lens barrel using the second and third assembly jigs for lens/framepositioning. FIGS. 6A, 6B, 6C are enlarged sectional views showing ashape of a bonding portion between the lens group and lens holding framein the lens barrel. FIG. 6A shows a case where the lens holding frame isprotruded relative to the lens. FIG. 6B shows a case where the lensgroup is protruded relative to the lens holding frame. FIG. 6C shows acase where the lens holding frame and the lens are located onsubstantially the same surface. FIG. 7 is a longitudinal sectional viewafter the lens barrel of the embodiment is assembled. FIG. 8 is asectional view taken along the line I—I of FIG. 7, indicating a partialsection of a portion around the guide shaft in the lens barrel. FIG. 9is a development view of a cam groove in cam ring applied to the lensbarrel of the embodiment.

In the above description, it is assumed that an object side of the lensbarrel is forward and an image side is backward. A rotation direction ofa cam ring or the like is indicated when viewed from forward (objectside).

The lens barrel 1 of this embodiment is incorporated in a zoom camera orused as an interchangeable type zoom lens barrel. As shown in FIG. 1 andthe like, the lens barrel 1 includes a float key 3 (see FIG. 7) whoserotation is restricted and which is supported so as to be capable ofbeing advanced or retracted, a cam ring 2 which is capable of beingadvanced and retracted together with the float key 3 and which issupported rotatably, a first group frame 4, which is a first frame(moving frame member) advanced or retracted relatively by the cam ring2, a first group lens (optical element) 21 held by the first group frame4, a focus holding frame 6, which is a second frame (moving framemember) advanced or retracted relatively by the cam ring 2, a focusframe 5, which is a fourth frame (moving frame member) advanced orretracted by a focus driving mechanism (not shown) relative to the focusholding frame 6, second group lens (optical element) including a secondgroup lens (front) 22, second group lens (middle) 23 and second grouplens (rear) 24, which are focus lenses held by the focus frame 5, and ashutter 15 incorporated in the focus frame 5. Further, the lens barrel 1includes a third group frame 7, which is a third frame member (movingframe) advanced or retracted relatively by the cam ring 2, a third grouplens (front) 25 and third group lens (rear) 26 composing the third lens(optical element) held by the third group 7, guide shafts 8, 9, whichare first guide members (first supporting members) for attachment tofocus holding frame 6 and supporting the first frame 4 and the thirdframe 7 slidably and a guide shaft 11, which is a second guide member(second supporting member) supported by the first group frame 4 andthird group frame 7 and for supporting the focus frame 5 slidablythrough a sleeve 10.

As shown in the development diagram of FIG. 9, the cam ring 2 has threepairs of cam portions in which a length direction of a groove thereofincludes of three rows along the rotation direction as shown in adevelopment diagram of FIG. 9.

Each pair of the aforementioned cam portion includes a cam groove 2 a inwhich a cam follower (will be described later) 4 i is fit slidably, acam groove 2 b in which a cam follower (will be described later) 6 i isfit slidably, a cam groove 2 c in which a cam follower (will bedescribed later) 7 i is fit slidably, a cam follower introducing groove2 d, which is an introducing portion for insertion of the aforementionedcam followers 4 i, 6 i, 7 i for assembly and a joint groove 2 e, whichis a joint portion for insertion of the cam follower 4 i for assembly.

The cam follower introducing groove 2 d is an introducing groove leadingfrom an opening portion 2 g in an end face 2 f on image side of the camring 2 to ends of the cam grooves 2 a, 2 c. The introducing groove 2 dis formed at an introducing position θA outside a tele end position θTof a rotation position of the cam ring 2, which will be described later,such that it is parallel to an optical axis O.

The joint groove 2 e is a joint portion connected to an end of the camgroove 2 a to an end of the cam groove 2 b. The joint groove 2 e isformed at a switch position θB outside a collapsed position θC of arotation position of the cam ring 2, which will be described later, suchthat it is parallel to the optical axis O.

The cam groove 2 c is provided on the image side of the cam ring 2 in arange from the introducing position θA to the switch position θB andincludes a collapsed range cam groove 2 c 1 existing inside that rangebetween the collapsed position θC and a wide end position θW and a zoomrange cam groove 2 c 2 existing between a wide end position θW and atele end position θT.

The aforementioned cam grooves 2 a, 2 b are joined through the jointgroove 2 e and are formed to extend side by side in a range from theintroducing position θA of the rotation position of the cam ring 2 tothe switch position θB. Then, the cam grooves 2 a, 2 b have collapsedrange cam grooves 2 a 1, 2 b 1 existing between the collapsed positionθC and the wide end position θW inside the aforementioned range and zoomrange cam grooves 2 a 2, 2 b 2 existing between the wide end position θWand tele end position θT.

Therefore, in a cam portion provided in the cam ring 2, the openingportion 2 g on the end face 2 f of the image side leads to the camfollower introducing groove 2 d. The introducing groove 2 d leads to thecam grooves 2 c and 2 b. The cam groove 2 b leads to the joint groove 2e. The joint groove 2 e lead to the cam groove 2 a.

The cam grooves 2 a, 2 b form a pair of continuous cam grooves connectedthrough the joint groove 2 e. Three pairs of the continuous cam groovesare provided in the cam ring 2. The aforementioned three pairs of thecontinuous cam grooves 2 a, 2 b are disposed in an inner circumferentialface of the cam ring 2 such that they overlap each other in the rotationdirection in a condition that they do not cross each other but invadeeach other.

The cam ring 2 incorporated in the lens barrel 1 is extended from thecollapsed position in the direction of the optical axis O along thefloat keys 3 by an extension driving mechanism (not shown) to aphotographing position. Further, the cam ring 2 is rotated from thecollapsed position θc to the wide end position θw by a zoom drivingmechanism (not shown).

Upon zooming operation, the cam ring 2 is rotated in an interval fromthe wide end position θw to the tele end position θt (see FIG. 9).Accompanied by the rotation, the cam follower is driven through each camgroove so that respective members of the first group frame 4 areadvanced or retracted. The position of the cam ring 2 indicated by therotation position (rotation angle) θ is indicated by a relative rotationposition of the aforementioned cam followers 2 a, 2 b, 2 c with respectto the cam follower rows (fixed).

The first group frame 4 includes an outer peripheral portion 4 j, abackward protruded lens holding portion 4 a, which is protruded alongthe optical axis and has a pawl portion 4 g, backward protruded bossportions 4 b, 4 c disposed at two positions up and down in the frameportion and extended along the optical axis, a shaft hole 4 f in which afront end of a guide shaft 11 is to be fit, and three cam followers 4 iattached to the outer peripheral portion and capable of entering the camgroove 2 a.

An inner circumference of the protruded lens holding portion 4 a has atolerance securing a gap for loose fitting with respect to an outercircumference of the first group lens 21 to be mounted. This gap is ofan appropriate dimension absorbing disparity of the dimensions ofrelating frames and lens member and a dimension allowing adhesive agentto be filled therein. Additionally, there is a gap in the optical axis Odirection between the position of the pawl portion 4 g and the face ofthe first group lens 21. That gap absorbs the disparity of the dimensionof the relating frames of the optical axis O and lens members and adimension allowing adhesive agent to be filled therein.

The boss portion 4 b has the shaft hole 4 d which the guide shaft 8 iscapable of being fit slidably when it is precision fit. On the otherhand, the boss portion 4 c has an long hole 4 e in which the guide shaft9 is capable of being fit slidably when it is precision fit around theoptical axis O. The aforementioned shaft hole 4 f is a hole having arelatively small depth in which the guide shaft 11 is fit when it isprecision fit.

Meanwhile, the precision fitting condition refers to a state in whichthere is no looseness between the hole portion and shaft portion or astate in which the fitting is attained with extremely little looseness.Fitting with loose, which will be described later, refers to a state inwhich the fitting is attained with a gap. Further, fitting slidably,which will be described later, refers to a fitting condition with aslight gap.

The focus holding frame 6 has shaft holes 6 a, 6 b disposed up and downin the frame portion and in which the guide shafts 8, 9 are fit withloose, an escape hole 6 c disposed sideways of the shaft hole 6 a andwhich the guide shaft 11 passes through, three cam followers 6 i capableof being fit into the cam groove 2 b, and a fitting innercircumferential portion 6 e. Further, the focus holding frame 6 containsa focus driving portion such as a feeding screw mechanism forfocus-driving the focus frame 5, which will be described later, (notshown).

The guide shafts 8, 9 are bonded into the shaft holes 6 a, 6 b with theassembly jig 31 for guide shaft positioning, which will be describedlater, in a positioning condition. The escape hole 6 c is an escape holein which a sleeve 10 is capable of entering with the guide shaft 11. Thefitting inner circumferential portion 6 e is capable of being fit to thefitting outer circumferential portion 5 f of the focus frame 5, whichwill be described, in a sliding condition.

The focus frame 5 includes lens holding portions 5 d and jig escapingportions 5 g, provided by dividing a front inner circumferential portioninto three parts, shutter incorporating concave portion 5 i and lensholding portion 5 j provided in the inner circumferential portion in thecenter, three protruded lens holding portions 5 e extended in theoptical axis direction provided in the rear and an outer circumferentialportion 5 f to be fit to the focus holding portion 6 provided on anouter circumference in the rear. Further, the focus frame 5 includes anescape portion 5 h for the guide shaft 8 disposed in an upper portion ofthe frame, a sleeve fitting hole 5 a disposed sideways of the escapeportion 5 h and U-shaped groove 5 c disposed in a lower portion of theframe and capable of being fit to and making a sliding contact with theboss portion 4 c of the first group frame 4 when it is precision fit.

The inner circumferences of the lens holding portion 5 d jig and lensholding portion 5 e have a tolerance of dimension containing a gap withrespect to the outer diameters of the second group lens (front) 22 andsecond group lens (rear) 24 to be mounted, thereby absorbing disparityof dimension of relating frames and lens members and providing asufficient gap allowing adhesive agent to be filled with.

A lens contacting face 5 k which makes a contact with a lens face of thesecond group lens (front) 22 to be mounted is provided in the rear inthe direction of the optical axis O of the lens holding portion 5 d.Further, a lens contacting face 5 m, which makes contact with a lensface of the second group lens (rear) 24, is provided forward in thedirection of the optical axis O of the lens holding portion 5 e.

The lens holding portion 5 j has an inner periphery which an outercircumference of the second group lens (middle) 23 is precision fit toand the second group lens (middle) 23 is directly bonded thereto.

The diameter of the sleeve fitting hole 5 a is as large as the sleeve 10can be fit thereto with loose, thereby absorbing disparity of dimensionof the relating frames and lens members and providing a dimensionallowing adhesive agent to be filled therein.

The third group frame 7 includes a front end face portion 7 h, an outerperipheral portion 7 g, lens holding portions 7 d and jig escapingportions 7 e divided to three sections by the front end face portion 7h, a shaft hole 7 a disposed in a upper portion and in which the guideshaft 8 is fit slidably in precision fitting condition, a long hole 7 bdisposed in a lower portion of the frame and which the guide shaft 9 isfit slidably in the direction of the optical axis O around the opticalaxis O in precision fitting condition, and a shaft hole 7 c relativelyshort disposed sideways of the shaft hole 7 a and which the guide shaft11 is precision fit.

Further, the third group frame 7 includes three cam followers 7 iattached to the outer peripheral portion 7 g and capable of being fit tothe cam groove 2 c and three advancement guide protrusions 7 f disposedon a rear flange of the outer peripheral portion 7 g.

Here, the reason why the aforementioned shaft hole 4 f and the shafthole 7 c are relatively short fitting holes will be described. Whilethese two shaft holes 4 f and 7 c are fit to the guide shaft 11, theguide shaft 11 is capable of being tilted slightly because such arelatively short fitting length is provided. How much the guide shaft 11is capable of being tilted depends upon a minimum distance between thefirst group frame 4 and the third group frame 7 and positionalaccuracies of the shaft holes 4 f, 7 c with respect to the guide shaftholes 4 d, 7 a in the first group frame 4 and third group frame 7. Thatis, it is largely relating to an error of a relative distance betweenthe guide shaft hole 4 d and the shaft hole 4 f and an error of arelative distance between the guide shaft hole 7 a and the shaft hole 7c. The guide shaft 11 needs to be tilted more as these two errors areabsorbed. Naturally, if these errors are small, the fitting accuracybetween the guide shaft 11 and the shaft holes 4 f, 7 c is intensified,so that if the fitting length is increased, the tiltable angle of theguide shaft 11 may be small. However, if these errors are large, thefitting accuracy must be lowered while the fitting length must beshortened. In this case, the assembly accuracy of the lens barrel drops.

In other words, the tiltable angle of the guide shaft is determined bythe aforementioned minimum distance and two errors. Then, the fittingaccuracy between the hole and guide shaft and the fitting length aredetermined. Generally, that angle should be determined by the fittinglength without lowering the fitting accuracy. That is, the guide shaft11 can be tilted by decreasing the fitting length.

An inner circumference of the lens holding portion 7 d has a toleranceof dimension having a gap with respect to the outer diameter of afitting portion of the third group lens (front) 25 to be mounted,thereby absorbing disparity of dimension of the relating frames and thelens member and providing a dimension allowing adhesive agent to befilled therein.

There is a gap in the direction of the optical axis between an inner endface 7 k of the lens holding portion 7 d and a flange face 25 a of thethird group lens (front) 25. That gap absorbs disparity of dimension ofthe relating frames and lens members and provides a sufficient gapallowing adhesive agent to be filled therein.

When assembling the lens barrel 1 of this embodiment having such astructure, the first assembly jig 31 for guide shaft positioning shownin FIG. 2, the second assembly jig 32 for lens/holding frame positioningshown in FIGS. 3, 4 and the third assembly jig 33 are used.

As shown in FIG. 2, the first assembly jig 31 for guide shaftpositioning has V-grooves 31 a, 31 b disposed up and down in an outerperiphery for holding the guide shafts 8, 9 at a predeterminedseparating distance in parallel to the optical axis O and an outercircumferential portion 31 c for positioning capable of being precisionfit to the fitting inner circumferential portion 6 e of the focusholding frame 6.

The second assembly jig 32 for lens/holding frame positioning is acylinder partitioned to front and rear by a wall portion (a backwardwall face 32 g is assumed to be 32 g) as shown in FIG. 3 and has aforward inner peripheral face 32 a and a backward inner peripheral face32 b. The forward inner peripheral face 32 a has a stopper 32 j forpositioning the focus holding frame 6 in the direction of the opticalaxis O.

A front face of the wall portion has three protruded lens supportingportions (inner peripheral face) 32 e which are protruded in thedirection of the optical axis and a lens contact face 32 f which isdisposed in the rear of the supporting portions. Further, a rear facethereof has three protruded lens supporting portions (inner peripheralface) 32 h, which are protruded in the direction of the optical axis anda lens contact face 32 i, which is disposed in front of the innerperipheral portion. Further, the aforementioned wall portion hasescaping holes 32 c, 32 d.

The forward inner peripheral face 32 a is an inner peripheral face whichthe outer peripheral portion 4 j of the first group frame 4 and theouter peripheral face 33 a of the assembly jig 33 are capable of beingprecision fit. The backward inner peripheral face 32 b is an innerperipheral face which the outer peripheral portion 7 g of the thirdgroup frame 7 is capable of being precision fit.

The lens supporting portions (inner peripheral face) 32 e, 32 h areinner peripheral faces which the outer peripheries of the second grouplens (rear) 24, third group lens (front) 25 are capable of beingprecision fit.

As shown in FIG. 4, the second assembly jig 33 for the lens/holdingframe positioning is a substantially circular jig having an outerperipheral face 33 a. Three divided protruded lens supporting portions33 b are provided such that they are protruded in the direction of theoptical axis and lens contact faces 33 c are provided in the rear ofeach inner peripheral portion. A rear face of the second assembly jig 33has three divided protruded lens supporting portions (inner peripheralfaces) 33 d, which are protruded in the direction of the optical axis,lens contact faces 33 e provided in the rear of each inner peripheralportion and escaping portions 33 f provided up and down in the outerframe.

Inner peripheral faces of the lens supporting portions 33 b, 33 d areinner peripheral faces which the outer peripheries of the first grouplens 21 and second group lens (front) are capable of being precisionfit.

To attach the guide shafts 8, 9 to the focus holding frame 6 whenassembling the lens barrel 1, as shown in FIG. 2, using the firstassembly jig 31, the outer circumferential portion 31 c for framepositioning is fit to the fitting inner circumferential portion 6 e ofthe focus holding frame 6.

Then, the guide shafts 8, 9 inserted through the shaft holes 6 a, 6 b inthe focus holding frame 6 are fixed in the V-grooves 31 a, 31 b of theassembly jig 31. Because the shaft holes 6 a, 6 b have a gap withrespect to the guide shafts 8, 9, the guide shafts 8, 9 are kept at apredetermined position in the direction of the optical axis with apredetermined distance between the shafts such that they are parallel tothe optical axis.

With the above supporting condition, adhesive agent (fixing agent) ispoured through adhesive agent pouring holes 6 f, 6 g in the focusholding frame 6 so as to fix the guide shafts 8, 9 in the shaft holes 6a, 6 b.

Next, the assembly jigs 32, 33 are employed in order to assemblerespective lens barrel components around the focus holding frame 6having the guide shafts 8, 9. Meanwhile, upon assembly, the assembly jig32 shown in FIG. 3 is inserted between insertion positions b1 and b2with respect to the lens barrel 1 shown in FIG. 1. Then, the assemblyjig 33 shown in FIG. 4 is inserted between insertion positions a1 and a2with respect to the lens barrel 1 shown in FIG. 1.

In the assembly jig 32 shown in the longitudinal sectional view of FIG.5, the outer peripheral face of the second group lens (rear) 24 is fitto the inner peripheral face of the lens supporting portion 32 e suchthat the second group lens face is in contact with the lens contact face32 f.

On the other hand, the outer peripheral face of the second group lens(front) 22 is fit to the inner peripheral face of the lens supportingportion 33 d of the assembly jig 33 such that the aforementioned lensface is brought into contact with the lens contact face 33 e.

Then, the focus holding frame 6 having the guide shafts is inserted upto a reference position where it comes into contact with a stopper 32 jof the assembly jig 32, on which the lens is mounted, from forward inthe direction of the optical axis.

Further, the fitting outer circumferential portion 5 f of the focusframe 5, to which the second group lens (middle) 23 is bonded, is fit tothe fitting inner circumferential portion 6 e of the focus holding frame6 and inserted until the lens contact face 5 m of the focus frame 5comes into contact with the front lens of the second group lens (rear)24. At this time, the aforementioned stopper of the jig is set such thatthe focus holding frame 6 is floated with a gap with respect to thestopper in the direction of the optical axis.

Then, the guide shafts 8, 9 are inserted into the escaping portion 5 hand U-groove 5 c in the focus frame 5. Further, the sleeve 10 isinserted into the sleeve fitting hole 5 a in the focus frame 5 andinserted into the escaping hole 6 c in the focus holding frame 6.

After that, the aforementioned assembly jig 33, on which the lens ismounted, is fit to the forward inner peripheral face 32 a of theassembly jig 32 and the rear lens face of the second group lens (front)22 is inserted until it comes into contact with the lens contact face 5k of the focus frame 5. At this time, the protrusion of the lenssupporting portion 33 d of the assembly jig 33 is fit into the escapingportion 5 g of the focus frame 5.

Then, the first group frame 4 is installed. Before the installation, theguide shaft 11 is inserted into the shaft hole 4 f in the first groupframe 4 and an E-ring 12 is embedded into an E-ring groove 11 a in afront end of the guide shaft (See FIG. 8). The guide shaft 11 is capableof being advanced or retracted with the first group frame 4 by thisE-ring 12.

The first group frame 4 with the guide shaft 11 is inserted up to areference position in the direction of the optical axis in front of theassembly jig 33, where it comes into contact with a stopper (not shown)of the assembly jig 32 or an end of the pawl portion 4 g of the firstgroup frame 4 comes into contact with the escaping portion 33 g in thejig 33. At this time, the guide shaft 8 is fit into the shaft hole 4 din the first group frame 4 and the guide shaft 9 is fit into the longhole 4 e in the first group frame 4.

Further, the boss portion 4 c of the first group frame 4 is fit into theU-groove 5 c of the focus frame 5. After fitting the sleeve 10 on thefocus frame 5, the guide shaft 11 is held such that it is passed throughthe escaping hole 6 c in the focus holding frame 6.

After that, if the first group lens 21 is inserted into the first groupframe 4, the first group lens 21 comes into contact with the lenscontact face 33 c of the jig 33 such that it is floated with respect tothe first group frame 4. Consequently, the outer circumference of thefirst group lens 21 is precision fit to the lens supporting portion 33 band supported by the jig 33.

Subsequently, the third group frame 7 is fit loosely to the backwardinner peripheral face 32 b of the assembly jig 32 and then inserted upto a reference position in the direction of the optical axis where anend face portion 7 h thereof comes into contact with the wall portion 32g. At that time, the guide shafts 8, 9, 11 are fit into the shaft hole 7a, long hole 7 b and shaft hole 7 c. The protrusion of the lenssupporting portion 32 h of the jig 32 is fit into the escaping portion 7e of the third group frame 7.

With the third group frame 7 inserted, the third group lens (front) 25is fit into the inner peripheral portion of the lens supporting portion32 h of the assembly jig 32 and a lens end face thereof is brought intocontact with the lens contact face 32 i for positioning.

With the respective lens barrel components set in the aforementionedassembly jigs 32, 33, the first group frame 4 and the third group frame7 are positioned at the optical axis O position at a predeterminedprecision in the direction of the optical axis O through the respectivefitting shaft holes by the guide shafts 8, 9 supported by the focusholding frame 6 (see FIG. 7). Further, a rotation phase position of thefocus frame 5 is determined at a predetermined precision around theoptical axis O through the boss portion 4 c of the first group frame 4(see FIG. 7).

On the other hand, the first group lens 21, second group lens (front)22, second group lens (rear) 24 and third group lens (front) 25 areprecision fit to the inner peripheral face of the lens supportingportion, which is divided to three parts, and centered by the assemblyjigs 32, 33. Additionally, they are brought into contact with thecontact portions so that they are positioned in the direction of theoptical axis O.

As described above, the respective lens groups are supported such thatthey are floated at an accurate position by the assembly jig 32.

Meanwhile, the outer peripheries of the first group frame 4 and thirdgroup frame 7 may be theoretically of a dimension allowing a loosefitting to the inner periphery of the jig 32. The reason is that thepositioning accuracy of the guide shafts 8, 9 has been alreadydetermined.

The lens holding portions, which are divided into three sections each,of the first group frame 4, focus frame 5 and third group frame 7 arelocated along a circumference of each of the corresponding lenssupporting inner peripheral faces, which are divided into three sectionseach, of the assembly jigs, 32, 33 and positioned with an appropriategap for adjustment or bonding with respect to the outer peripheral faceof each lens.

Further, with respect to a lens face of each lens in the direction ofthe optical axis O, there is an appropriate gap for adjustment of aposition in the direction of the optical axis O and bonding between thepawl portion 4 g of the first group frame 4 or the lens holding end face7 k of the third group frame 7 and a flange face (flange face 25 a ofthe third group lens 25) of each lens.

The guide shaft 11 fit and inserted into the focus frame 5 through thesleeve 10 supported with loose is maintained in an appropriate conditionin the shaft hole even if there is disparity in the shaft hole betweenthe first group frame 4 and third group frame 7 positioned by the guideshafts 8, 9.

If a leaf spring type lens holding mechanism or the like is incorporatedto prevent deviation or slip-out of each lens mounted on the lenssupporting portion although it is not indicated on each lens supportingportion of each of the assembly jigs 32, 33 shown in FIGS. 3, 4,assembly efficiency is further improved.

The sleeve and lens of the lens barrel 1 are bonded with adhesive agent(fixing agent) in a setting condition by the assembly jigs 32, 33.

First, bonding of the sleeve 10 is carried out by pouring adhesive agentthrough the adhesive agent pouring hole 5 b leading to the sleevefitting hole 5 a provided in the outer peripheral portion of the focusframe 5.

Bonding of the first group lens 21 is carried out by pouring adhesiveagent into a lens holding gap S1 formed by the lens holding portion 4 a,pawl portion 4 g and first group lens 21 through an opening hole 4 k, 4l provided in the outer periphery of the first group frame 4 and thelens holding portion 4 a (see FIG. 5).

Instead of the pouring of the adhesive agent, it is permissible to coatthe lens holding portion 4 a of the first group frame 4 with adhesiveagent for the bonding.

Bonding of the second group lens (front) 22 is carried out by applyingadhesive agent onto the lens holding portion 5 d of the focus frame 5preliminarily and then filling a lens holding portion gap S2 formed bythe lens holding portion 5 d, lens contact face 5 k and the outerdiameter of the second group lens (front) 22 with adhesive agent.

Bonding of the second group lens (rear) 24 is carried out by pouringadhesive agent into a lens holding portion gap S3 formed by the lensholding portion 5 e, lens contact face 5 m and the outer diameter of thesecond group lens (rear) 24 through an opening hole 32 k provided in theouter periphery of the assembly jig 32.

Instead of the pouring of the adhesive agent, it is permissible to coatthe lens holding portion 5 e of the focus frame 5 with adhesive agentfor the bonding.

Bonding of the third group lens (front) 25 is carried out by applyingadhesive agent onto the lens holding portion 7 d of the third groupframe 7 preliminarily and filling a lens holding portion gap S4 formedby the lens holding portion 7 d, inside end face 7 k and the outerdiameter of the third group lens(front) 25 with adhesive agent throughan opening (not shown) provided in the outer periphery of the assemblyjig 32.

Here, by bringing the third group lens (rear) 26 into contact with arear side face of the third group lens (front) 25, adhesive agent isapplied into a gap between the inner peripheral face 7 m formed thethird group frame 7 and the outside diameter of the third group lens(rear) 26 for bonding.

When installing the third group lens (rear) 26, it is permissible toinstall the third group lens (rear) 26 while observing and adjustingalignment thereof entirely with the first group lens 21, second grouplenses 22, 23, 24 and the third group lens (front) 25. Alternatively, itis permissible to mount the third group lens (rear) 26 while observingand adjustment alignment thereof with respect to assembly of the thirdgroup lens (front) 25 having no third group lens (rear) 26 and the thirdgroup frame 7.

Meanwhile, if the lens holding portion is filled with adhesive agent,there is a fear that the adhesive agent may flow out to the surface ofthe lens so that its optical performance may be damaged. Therefore, asshown in FIGS. 6A, 6B, 6C, the lens end face and/or lens holding endface is provided with a chamfered portion so as to prevent a flow out ofadhesive agent.

That is, when the lens holding portion is protruded from a lens, forexample, as shown in FIG. 6A, an end face 7 h of the lens holdingportion 7 d of the third group lens 7 is protruded from the third grouplens (front) 25. Thus, a chamfered portion 25 a is provided on an endface of the third group lens 25. By employing this configuration,adhesive agent 44 loaded in the gap S4 hardly flows out from the gap S4to the surface of the lens.

Further, when the lens is protruded from the lens holding portion, forexample, as shown in FIG. 6B, the second group lens (front) 22 isprotruded from an end face of the lens holding portion 5 d of the focusframe 5. Thus, a chamfered portion 5 n is provided on an end face of thelens holding portion 5 d. By employing this configuration, adhesiveagent 42 loaded in the gap S2 hardly flows out from the gap S2 to thesurface of the lens.

Further, a state in which the lens holding portion and the lens arelocated on the same plane never exists in the lens barrel 1 of thisembodiment. Because as shown in FIG. 6C, for example, the end face ofthe lens holding portion 13 d of the lens frame 13 and the lens 27 arelocated on the same plane if this state is attained, both the end faceof the lens holding portion 13 d and the outer periphery of the lens 27are provided with the chambered portions 13 a, 27 a. By employing thisconfiguration, the adhesive agent 45 loaded in this gap S5 hardly flowsout of the gap S5 to the surface of the lens.

If mounting and bonding of the guide shafts, lens and the like by theassembly jigs 32, 33 shown in FIG. 5 are finished, the jigs 32, 33 areremoved from the lens barrel 1. At that time, the third group frame 7 isremoved from the jig 32 and the first group frame 4 is removed fromfront with the guide shaft 11.

After the assembly jig 33 is also removed from front, the focus frame 5and focus holding frame 6 are removed from the assembly jig 32 with theguide shafts 8, 9. FIG. 7 shows a longitudinal sectional view of thelens barrel 1 in a condition that the assembly jigs 32, 33 are removedto assemble those lens frames.

The reason why the removal of the lens barrel 1 is enabled even if theassembly jig 32 having the wall portion (wall face 32 g) is used, asdescribed above, is due to the supporting structure of each guide shaft.That is, the guide shaft 11 is supported by the side of the first groupframe 4 and the other frame members are supported slidably. Further, theguide shafts 8, 9 are supported by only the focus holding frame 6disposed in the center and supported slidably by the other framemembers.

After the above described installation is finished, the cam ring 2 isincorporated in the lens barrel 1 and then, the first group frame 4, thefocus holding frame 6 and three cam followers 4 i, 6 i, 7 i of the thirdgroup frame 7 are fit into the three sets of the cam grooves 2 a, 2 b, 2c in the cam ring 2.

Upon zoom driving, the cam ring 2 is driven from the collapsed positionθC indicated by a rotation position with respect to the cam follower tothe tele end position θT. As shown in FIG. 9, the cam followerintroducing groove 2 d is provided at an introduction position θA, whichis a rotation position outside the tele end position θT. Further, ajoint groove 2 e for the cam follower to move is provided at a switchposition θB, which is a rotation position outside the other collapsedposition θC.

Then, in the respective cam grooves, the cam follower introducing groove2 d and the joint groove 2 e are joined to each other and those camgrooves are disposed around the optical axis O such that they are formedto extend side by side in a length direction thereof and the cam groove2 a, cam groove 2 b and cam groove 2 c are arranged in this order fromthe object side.

The cam follower introducing groove 2 d is a groove in the direction ofthe optical axis O provided for joining the tele side end portions ofthe cam groove 2 b and cam groove 2 c and its insertion mouth is open toa rear side. The joint groove 2 e is a groove in the direction of theoptical axis O for joining the collapsed side end portions of the camgroove 2 a and the cam groove 2 b.

When fitting the cam follower into the above described cam grooves, thecam follower introducing groove 2 d and the joint groove 2 e are used.

First, the cam follower 4 i of the first group frame 4 shown in FIG. 7is positioned at a cam ring insertable position and then, the cam ring 2is rotated up to the introduction position θA so as to be inserted intothe lens barrel 1. Then, the cam follower 4 i enters from the openingportion 2 g of the cam ring 2 into the cam follower introducing groove 2d.

If the cam follower 4 i reaches the end position of the cam groove 2 b,the cam ring 2 is rotated clockwise up to the switch position θB. Bythat rotation, the cam follower 4 i passes the cam groove 2 b andreaches the joint groove 2 e. Then, the cam ring 2 is pushed relativelyto the rear side of the lens barrel so that the cam follower 4 i is fedto the end position of the cam groove 2 a on the front side. Next, thecam ring 2 is rotated counterclockwise so as to be returned to theintroduction position θA.

Next, the cam followers 6 i, 7 i of the focus holding frames 6 and thethird group frame 7 are set in the cam ring insertable position. Next,if the cam ring 2 is pushed relatively to the rear side of the lensbarrel, the cam followers 6 i, 7 i enter from the opening portion 2 g ofthe cam ring 2 into the cam follower introducing groove 2 d.

Then, if the cam follower 6 i reaches the position of the cam groove 2 band the cam follower 7 i reaches the position of the cam groove 2 c, thecam ring 2 is rotated clockwise. The cam follower 6 i enters the camgroove 2 b and the cam follower 7 i enters the cam groove 2 c. Meanwhilethe cam follower 4 i is kept in the cam groove 2 a and then, enteringthe cam groove of each cam follower into the cam ring 2 is finished.

After that, the guide protrusion 7 f of the third group frame 7 is fitinto an advancement guide groove 3 a provided in the front key 3 andthen, the third group frame 7 is kept capable of being advanced orretracted while its rotation is restricted by the front key 3.Consequently, the assembly of the lens barrel 1 of this embodiment isfinished.

When the lens barrel 1 is in the collapsed condition, the cam ring 2 isrotated to the collapsed position θC shown in FIG. 9 and further,introduced to the collapsed position in the direction of the opticalaxis O.

Then, the cam ring 2 is introduced up to a photographing possibleposition along the optical axis O and the collapsed region A1 (see FIG.9) is rotated counterclockwise to the wide end position θW through thezoom driving portion. By this rotation, the respective cam followers 4i, 6 i, 7 i are advanced or retracted relatively by the cam grooves 2 a,2 b, 2 c. The first group frame 4 and the focus holding frame 6 and thethird group frame 7 are moved to the zoom wide end position enablingphotographing along the optical axis O.

If the cam ring 2 is zoom driven throughout the zoom region A2 (see FIG.9) up to the tele end position θT by the aforementioned zoom drivingportion, the respective cam followers 4 i, 6 i, 7 i are advanced orretracted relatively by the cam grooves 2 a, 2 b, 2 c. Consequently, thefirst group frame 4, the focus holding frame 6 and third group frame 7are moved from the zoom wide end position to the zoom tele end positionalong the optical axis O.

The focusing drive of the lens barrel 1 is carried out by advancing orretracting the focus frame 5 relative to the zoom-driven focus holdingframe 6 along the optical axis O by means of a focus driving portion(not shown).

In the lens barrel 1 of an embodiment described above, the first groupframe 4, the focus frame 5, the focus holding frame 6, and third groupframe are supported by the guide shafts 8, 9 and 11 such that they arecapable of being advanced or retracted. The guide shafts 8, 9 are fixedat the focus holding frame 6 located substantially in the center andboth ends of the guide shafts 8, 9 are slidable with respect to thefirst group frame 4 and third group frame. In other words, the firstgroup frame and third group frame are capable of sliding in thedirection of the optical axis at both ends of the guide shafts 8, 9.

Therefore, as compared to a conventional type in which the frame membersare supported by the lens barrel such that both ends of the guide shaftsare fixed to the frame members, a restriction of moving space for thefirst group frame and third group frame is decreased, therebycontributing to reduction of the size. Further, as compared tocantilever type in which an end of the guide shaft is fixed andsupported by conventional the lens barrel, the shaft span is shortenedso that distortion is decreased. Consequently, more accurateadvancement/retraction drive of the frame member can be realized.Further, the diameter of the guide shaft can be decreased thereby alsocontributing to reduction of the size of the lens barrel.

Further, the guide shaft 11 supports the focus frame 5, whose rotationaround the guide shaft 11 is restricted by the boss portion 4 c of thefirst group frame 4, slidably through the sleeve 10. An end of the guideshaft 11 is supported by the shaft hole 4 f of the first group frame 4as shown in FIG. 8 and the other end is supported freely slidably by theshaft hole 7 c of the third group frame 7. Further, because the fittinglengths of the shaft holes 4 f, 7 c are short and an inclination of theguide shaft 11 has a freedom so that it is capable of being unparallelto the guide shafts 8, 9, a disparity and error of dimension of thefirst group frame 4 or third group frame 7 can be absorbed not toobstruct a motion of the first group frame 4 and third group frame 7.

Further, if the diameter of the guide shaft 11 is small, a high loadtorque is applied between the focus frame 5 and the focus holding frame6 when the focusing is driven. At this time, if the guide shaft 11 isabout to be twisted largely, the focus frame 5 is prevented from beingdeviated largely, because the fitting outer circumferential portion 5 fof the focus frame and the fitting outer circumferential portion 6 e ofthe focus holding frame are fit to each other slidably.

According to the present invention, even if the dimensional accuraciesof the respective frame members are decreased to some extent within anallowable range, a high accuracy as the lens barrel is maintained,thereby contributing to reduction of production cost of the parts. Atthe same time, because the respective members can be installed to theguide members in a relatively easily movable condition, the assemblythereof is facilitated. Further, because only three shafts are employedas the guide members for supporting the four frame members, an occupiedspace is small, thereby making it possible to produce a small lensbarrel.

What is claimed is:
 1. A lens barrel comprising: a first frame; a secondframe; a third frame; and a first supporting member fixed to said secondframe with both ends thereof exposed, wherein said both ends thereofsupport said first and third frames.
 2. A lens barrel as claimed inclaim 1 wherein said first frame is supported movably by said firstsupporting member.
 3. A lens barrel as claimed in claim 1 wherein saidsecond frame is supported by said first supporting member and the secondframe is movable integrally with said first supporting member.
 4. A lensbarrel as claimed in claim 1 wherein said third frame is supportedmovably by said first supporting member.
 5. A lens barrel as claimed inclaim 1, further comprising an optional axis, wherein at least one ofsaid first frame, said second frame and said third frame is movable in adirection of the optical axis.
 6. A lens barrel as claimed in claim 1wherein said first supporting member is a bar-like member.
 7. A lensbarrel as claimed in claim 1 further comprising: a second supportingmember supported by said first frame and said third frame; and a fourthframe supported by said second supporting member, said fourth framebeing movable relatively between said first frame and said second frame.8. A lens barrel as claimed in claim 7 wherein said fourth frame has asleeve member and said second supporting member is fit to said sleevemember so as to support said fourth frame.
 9. A lens barrel as claimedin claim 8 wherein said sleeve member is capable of being fit to a holewith loose fitting provided in said second frame in non-contactcondition.
 10. A lens barrel as claimed in claim 7 wherein said secondsupporting member is supported tiltably relative to said first frame andsupported slidably by said third frame.
 11. A lens barrel as claimed inclaim 7 wherein an end of said second supporting member is precision fitto said first frame and the other end of said second supporting memberis precision fit to said third frame while fitting lengths thereof areshort.
 12. A lens barrel as claimed in claim 8 wherein said sleevemember is fit to a hole with loose fitting provided in said fourth frameand bonded.
 13. A lens barrel comprising: frame members; and a bar-likeguide member fixed to one of the frame members between both end portionsof the bar-like guide member, said both end portions supporting otherframe members slidably relative to one of the frame members.
 14. A lensbarrel as claimed in claim 13 wherein the frame member on which saidguide member is fixed is a movable frame.
 15. A lens barrel comprising:a first frame member movable within the lens barrel; a second framemember movable within the lens barrel; a third frame member movablewithin the lens barrel; and a first guide member including a bar-likemember, having two end face portions wherein a central portion of thebar-like member supports said second frame member while one end faceportion thereof guides said first frame member and the other end faceportion guides the third frame member.
 16. A lens barrel as claimed inclaim 15 further comprising: a second guide member supported by saidfirst frame member and said third frame member; and a fourth framemember guided by said second guide member so that said fourth framemember is movable relatively between said first frame member and saidsecond frame member.
 17. A lens barrel as claimed in claim 16 whereinsaid fourth frame member has a sleeve member and said second guidemember is fit to said sleeve member so as to guide said fourth framemember.
 18. A lens barrel as claimed in claim 17 wherein said sleevemember is capable of being fit to a hole with loose fitting provided insaid second frame member in non-contact condition.
 19. A lens barrel asclaimed in claim 16 wherein said second guide member is supportedtiltably by said first frame member and supported slidably by said thirdframe member.
 20. A lens barrel as claimed in claim 16 wherein an end ofsaid second guide member is precision fit to said first frame member andthe other end of said second guide member is precision fit to said thirdframe member while the fitting lengths are short.
 21. A lens barrel asclaimed in claim 17 wherein said sleeve member is fit to and bonded to ahole with loose fitting provided in said fourth frame member.